vSL is a lightweight scripting language dedicated to email filtering. It is based on the Rhai scripting language, and simply adds helper syntax and functions on top of it.
Advanced users can use the Rhai scripting language on top of vSL to create and manage a wide variety of actions. You can check out the Rhai reference book to learn everything you can do with this language, but for now, if you just want to learn the gist of how the rule system works, follow this section.
To interact with the SMTP traffic, vSL combines:
- filtering rules.
- Configuration-like objects
- email utilities wrapped in functions.
- services to interact with third-party software
Rules can be applied at any stage of the SMTP transaction.
The delivery system uses the same concepts by applying rules to targeted domains and users.